“Isis thrives on propaganda and radicalising young people by various means so, I’ve said all along, Ireland is not immune from any threat, but the evidence we have to date is that an attack is possible, but not likely.

“As a democratic western country, Isis is targeting the whole of western Europe effectively.”

Mr Mair said the inclusion of the Irish flag in the coalition “would suggest that IS views Ireland as a legitimate target for violence”.

He said the International Centre for the Study of Radicalisation had estimated around 30 people from Ireland had travelled to Syria or Iraq to fight. He said it was unclear how many had returned home.

He also said Ireland had around 150 soldiers in the Golan region, bordering Syria and Israel, as part of the UN Peacekeeping Mission to Syria.

“While this is not IS-held territory, any Western military intervention in ‘Muslim land’ is seen as an invasion by imperialist crusaders and legitimises violence against them,” Mr Mair said.

“For that reason, an IS supporter in Ireland may very well take the inclusion of the Irish flag in the ‘coalition of enemies’ as a green light for a terror attack.”

He said the video was aimed, in part, at Western Muslims interested in leaving their homes and travelling to Syria and Iraq, particularly those who felt excluded in their homelands.

“The 60 countries outlined in the image of the national flags share in this threat.”